1. Field of the Disclosure
The disclosure generally relates to a coating module, and more particularly, to a coating module able to change the plates thereof.
2. Description of Related Art
In recent years, in industrial processes, a coating device is often used to perform film-coating process, for example to form a raw strip on a ceramic capacitor or to coat optical protection film on a substrate. Taking a slot-type coating device as an example, the slot-type coating device is suitable for a film-coating process of large area. The coating device has a restrictor, and liquid is conveyed into the coating device by a measuring pump, and then outflows from a slot outlet of the coating device. The measuring pump can provide a stable supply of liquid. Therefore, the degree of uniformity for the coating liquid of the coating device will depend on the smoothness of the surface of the restrictor.
The coating device is generally formed by using two stainless steel modules to hold a shim. The shim has a restrictor and a diversion structure connecting the restrictor thereon, in which the diversion structure is, for example, a flow channel or a manifold so as to guide the liquid into the restrictor. The diversion structure mainly includes three types: T-die type structure, fishtail type structure and coat-hanger type structure. The processing and fabrication of the T-die type structure are more easily and able to make the flow rate of the liquid uniformly distributed, but the liquid is easy to form residue at the end of the manifold. The fishtail type structure enables the liquid to be uniformly spread in the flow channel, but the liquid is easy to form a recirculation zone in the diversion structures to affect the flow rate. The coat-hanger type structure can reduce the problems for the T-die type structure and the fishtail type structure to respectively produce the residue zone or the recirculation zone, but they are disadvantageous in complicate design and higher production cost. Therefore, the film-coating process usually employs a coating device with different diversion structure according to the coating liquid characteristic and the coating method, which makes a coating device very difficult to be shared for different film-coating processes.
On the other hand, in order to uniformly coating with a liquid by a coating device, the surface of the shim used to form the diversion structure and the restrictor, particularly the surface of the restrictor, must have high smoothness. Therefore, the shim requires lapping and polishing to increase the surface smoothness thereof. And, if the shim has a diversion structure with more complicate design, the shim needs for additional machining on each processing surface followed by lapping and polishing, so that the liquid can flow on the shim uniformly. These processes increase the manufacturing cost of the coating device. Further, when the restrictor of such a coating device gets worn, it is necessary to replace the shim to ensure the uniformity of the coating fluid. Thus, such a coating device has higher manufacturing costs, which accordingly indirectly increases the production cost of the products by using these coating devices for film-coating process.